Gas is becoming more and more attractive fuel for ships' prime movers and auxiliary engines. Particularly natural gas (NG) is feasible due to is availability. In ambient circumstances it is a gaseous mixture consisting primarily of methane and small amounts of ethane, propane, butane and nitrogen. It has high hydrogen content relative to coal, so when combusted it provides inter alia low emissions, very clean burning process and it's basically free of contaminants. Particularly in cruise vessels, ferries and ropax vessels, where passengers are on board, the absence of soot emissions and visible smoke in the exhaust of ship's engines is very important feature facilitated by using NG as fuel for the engines. Usually natural gas is stored as liquefied natural gas (LNG) at temperature of −162° C., thus the storage cause problems particularly when the LNG is stored at high pressure, about at 5 bar, which is typically the level that a gas operated piston engine requires. Considering that the tanks must be in that case pressure vessels, which usually are built in cylindrical form, and that the volume of the tanks could be at the magnitude of say 500-1000 m3, arranging large cylindrical tanks in a ship having spaces with basically rectangular cross section creates a lot of wasted space.
An object of the invention is to provide a fuel system for gas driven vessel, which solves the above mentioned and other problems of the prior art.
Object of the invention are met substantially as is disclosed in claim 1. The other claims present more details of different embodiments of the invention.